Fishes

4 pages, 150 KB

Open AccessEditorial

Sustainable Innovations in Shrimp Aquaculture: Current Advances and Future Horizons

by Wujie Xu

Fishes 2025, 10(10), 498; https://doi.org/10.3390/fishes10100498 - 3 Oct 2025

Abstract

With global seafood demand projected to increase by 38% by 2050 [...] Full article

(This article belongs to the Special Issue Advances in Shrimp Aquaculture: Management and Sustainability)

4 pages, 133 KB

Open AccessEditorial

Underwater Acoustic Technologies for Sustainable Fisheries

by Jianfeng Tong, Yong Tang and Tohru Mukai

Fishes 2025, 10(10), 497; https://doi.org/10.3390/fishes10100497 - 3 Oct 2025

Abstract

Underwater acoustic technologies have emerged as indispensable tools for advancing research, management, and conservation across aquatic ecosystems [...] Full article

(This article belongs to the Special Issue Underwater Acoustic Technologies for Sustainable Fisheries)

16 pages, 1811 KB

Open AccessArticle

Nanopore-Based Metagenomic Approaches for Detection of Bacterial Pathogens in Recirculating Aquaculture Systems

by Diego Valenzuela-Miranda, María Morales-Rivera, Jorge Mancilla-Schutz, Alberto Sandoval, Valentina Valenzuela-Muñoz and Cristian Gallardo-Escárate

Fishes 2025, 10(10), 496; https://doi.org/10.3390/fishes10100496 - 2 Oct 2025

Abstract

The microbial community in a recirculating aquaculture system (RAS) is pivotal in fish health, contributing significantly to the productive performance during the growing-out phase. Classical and molecular methods using PCR for species-specific amplifications have traditionally been used for bacterial community surveillance. Unfortunately, these [...] Read more.

The microbial community in a recirculating aquaculture system (RAS) is pivotal in fish health, contributing significantly to the productive performance during the growing-out phase. Classical and molecular methods using PCR for species-specific amplifications have traditionally been used for bacterial community surveillance. Unfortunately, these approaches mask the real bacterial diversity and abundance, population dynamics, and prevalence of pathogenic bacteria. In this study, we explored the use of Oxford Nanopore Technology to characterize the microbiota and functional metagenomics in a commercial freshwater RAS. Intestine samples from Atlantic salmon (Salmo salar (85 ± 5.7 g)) and water samples from the inlet/outlet water, settling tank, and biofilters were collected. The full-length 16S rRNA gene was sequenced to reconstruct the microbial community, and bioinformatic tools were applied to estimate the functional potential in the RAS and fish microbiota. The analysis showed that bacteria involved in denitrification processes were found in water samples, as well as metabolic pathways related to hydrogen sulfide metabolism. Observations suggested that fish classified as sick exhibited decreased microbial diversity compared with fish without clinical symptomatology (p < 0.05). Proteobacteria were predominant in ill fish, and pathogens of the genera Aeromonas, Aliivibrio, and Vibrio were detected in all intestinal samples. Notably, Aliivibrio wodanis was detected in fish showing abnormal clinical conditions. Healthy salmon showed higher contributions of pathways related to amino acid metabolism and short-chain fatty acid fermentation (p < 0.05), which may indicate more favorable fish conditions. These findings suggest the utility of nanopore sequencing methods in assessing the microbial community in RASs for salmon aquaculture. Full article

(This article belongs to the Special Issue Infection and Detection of Bacterial Pathogens in Aquaculture)

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19 pages, 2069 KB

Open AccessArticle

Ecology of River Dolphins and Fish at Confluence Aggregations in the Peruvian Amazon

by Richard Bodmer, Peter Henderson, Claire Spence, Tara A. O. Garraty, Kimberlyn Chota, Paola Uraco, Miguel Antunez, Tula Fang, Jack Butcher, Jake E. Bicknell, Osnar Pizuri and Pedro Mayor

Fishes 2025, 10(10), 495; https://doi.org/10.3390/fishes10100495 - 2 Oct 2025

Abstract

Amazon River dolphins often form multi-species aggregations at water confluences. This study used a multi-year data set to examine dolphins, fish, and geomorphology at dolphin aggregations. Methods included dolphin transect surveys, dolphin point counts, net and line fish captures, side-scan sonar, and eDNA [...] Read more.

Amazon River dolphins often form multi-species aggregations at water confluences. This study used a multi-year data set to examine dolphins, fish, and geomorphology at dolphin aggregations. Methods included dolphin transect surveys, dolphin point counts, net and line fish captures, side-scan sonar, and eDNA analyses at five dolphin aggregations and two control sites. Amazon River dolphins (Inia geoffrensis and Sotalia fluviatlis) are typically found at aggregation sites that occur at water confluences that have greater dolphin numbers than control sites. The confluences had riverbed depressions averaging six metres in depth where fish were concentrated. Pink river dolphins preferred to form aggregations in flooded forest tributaries and large rivers, while grey river dolphins preferred the larger rivers. There were eighty-nine fish species at the confluences within the size of fish consumed by dolphins, and a higher abundance of fish occurred in and around the aggregation sites compared to control sites. The number of dolphins present at the aggregation sites correlated with fish abundance. Dolphin life history, such as fishing, resting, raising calves, and social interactions, occur at the aggregation sites. The aggregation sites are important conservation areas of the endangered pink and grey river dolphins, and through their folklore, Indigenous people living at confluence sites assist in the conservation of the aggregations and have lived with dolphins at confluences for thousands of years, contributing to their survival. Full article

(This article belongs to the Section Biology and Ecology)

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27 pages, 8742 KB

Open AccessArticle

Bias-Adjusting Observer Species Composition Estimates of Tuna Caught by Purse-Seiners Using Port-Sampling Data: A Mixed-Effects Modeling Approach Based on Paired Well-Level Data

by Cleridy E. Lennert-Cody, Cristina De La Cadena, Luis Chompoy, Mark N. Maunder, Daniel W. Fuller, Ernesto Altamirano Nieto, Mihoko Minami and Alexandre Aires-da-Silva

Fishes 2025, 10(10), 494; https://doi.org/10.3390/fishes10100494 - 2 Oct 2025

Abstract

For large-scale tropical tuna purse-seine fisheries, it is prohibitively costly to obtain adequate sampling coverage to estimate fleet-level catch composition solely from sample data. Logbook or observer data, with complete fleet coverage, are often available but may be considered unreliable for species composition. [...] Read more.

For large-scale tropical tuna purse-seine fisheries, it is prohibitively costly to obtain adequate sampling coverage to estimate fleet-level catch composition solely from sample data. Logbook or observer data, with complete fleet coverage, are often available but may be considered unreliable for species composition. Previous studies have developed models, trained with sample data, to predict set-level species compositions based on environmental and operational covariates. Here, models were developed to predict well-level species composition from uncorrected observer data and covariates affecting the observers’ view of the catch during loading, with port-sampling data as the response variable. The analysis used paired, well-level data from sets made on floating objects by the Eastern Pacific Ocean tuna purse-seine fleet during 2023–2024. Results indicated that, overall, observer data proportions of bigeye (BET) and yellowfin tunas tended to be greater than the model-estimated proportions, with the opposite occurring for skipjack tuna (SKJ). However, vessel effects sometimes modified these tendencies. Model complexity was greatest for BET and least for SKJ. For BET, observer data proportions and model-estimated proportions were more similar when the vessel had a hopper. They were also more similar in 2023 as compared to 2024, suggesting sample data for bias adjustments should be collected annually. The approach shows potential for predicting the species composition of unsampled wells. Full article

(This article belongs to the Special Issue Fishing Gear Technology and Conservation of Fishery Resources)

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16 pages, 7302 KB

Open AccessArticle

circRNA Profiling Reveals Regulatory Networks Underlying Gonadal Differentiation in Nile Tilapia (Oreochromis niloticus)

by Mengfan Wu, Shangqi Li, Shen Huang, Wenzheng Sun, Xingxing Guo, Yanbin Zhang, Yiyun Du, You Wu, Linyan Zhou and Jian Xu

Fishes 2025, 10(10), 493; https://doi.org/10.3390/fishes10100493 - 2 Oct 2025

Abstract

The Nile tilapia (Oreochromis niloticus), a key aquaculture species, displays marked sexual growth dimorphism, with males growing faster than females. This process is governed by intricate interactions between antagonistic regulators, including transcription factors, growth factors, and steroid hormones, operating through sex-specific [...] Read more.

The Nile tilapia (Oreochromis niloticus), a key aquaculture species, displays marked sexual growth dimorphism, with males growing faster than females. This process is governed by intricate interactions between antagonistic regulators, including transcription factors, growth factors, and steroid hormones, operating through sex-specific developmental pathways. While circular RNAs (circRNAs) are known to modulate gene expression by sponging microRNAs (miRNAs), their role in teleost sex differentiation remains poorly understood. To address this gap, we profiled circRNA expression in tilapia gonads by constructing six circRNA libraries from testes and ovaries of 180 days after hatching (dah) fish, followed by high-throughput sequencing. We identified 6564 gonadal circRNAs distributed across all 22 linkage groups, including 226 differentially expressed circRNAs (DECs; 108 testis-biased, 118 ovary-biased). Functional enrichment analysis linked their host genes to critical pathways such as cAMP signaling, cell adhesion molecules, and—notably—sexual differentiation processes (e.g., estrogen signaling, oocyte meiosis, and steroid hormone biosynthesis). Furthermore, we deciphered competing endogenous RNA (ceRNA) networks, uncovering circRNA–miRNA–mRNA interactions targeting germ cell determinants, sex-specific transcription factors, and steroidogenic enzymes. This study provides the first systematic exploration of circRNA involvement in tilapia sex differentiation and gonadal differentiation, offering novel insights into the post-transcriptional regulation of sexual dimorphism. Our findings advance the understanding of circRNA biology in fish and establish a framework for future studies on aquaculture species with similar reproductive strategies. Full article

(This article belongs to the Special Issue Molecular Mechanisms of Fish Sex Differentiation and Sexual Plasticity)

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18 pages, 1665 KB

Open AccessArticle

Anthropogenic Microparticles in Aquaculture and Wild Fish: A Case Study of Three Commercially Important Species in the Eastern Mediterranean

by Aikaterini Kostoula, Eugenia Moschou-Kounopioti, Niki Milatou and Persefoni Megalofonou

Fishes 2025, 10(10), 492; https://doi.org/10.3390/fishes10100492 - 2 Oct 2025

Abstract

Over the past decade, increasing attention has been given to the impacts of anthropogenic microparticle (AM) pollution on marine ecosystems. This study investigates AM ingestion in three commercially important fish species—Sparus aurata Linnaeus, 1758, Dicentrarchus labrax Linnaeus, 1758, and Boops boops Linnaeus, [...] Read more.

Over the past decade, increasing attention has been given to the impacts of anthropogenic microparticle (AM) pollution on marine ecosystems. This study investigates AM ingestion in three commercially important fish species—Sparus aurata Linnaeus, 1758, Dicentrarchus labrax Linnaeus, 1758, and Boops boops Linnaeus, 1758—collected from both wild and farmed populations in Greek marine and lagoon environments. A total of 60 specimens were sampled from the Messolonghi Lagoon, Rhodes Island, and the Cyclades. AM were detected in 61.7% of the individuals analyzed. The mean number of ingested items per individual was 1.1 ± 1.2 in B. boops, 1.0 ± 1.7 in wild and 2.3 ± 2.1 in farmed S. aurata, and 2.5 ± 3.1 in wild and 3.6 ± 2.2 in farmed D. labrax. Ingestion ranged from 0 to 9 items per fish. No significant correlations were found between fish size and either the number or the size of ingested AM in any species. The ingested AM were primarily classified as fibers and fragments, displaying variability in size and color. Black was the dominant color across all species, followed by red and blue, while yellow was rarely observed. A statistically significant difference in the mean size of AM was recorded between wild and farmed D. labrax, whereas no such difference was observed for S. aurata. Overall, these findings provide new evidence on AM contamination in seafood species and highlight their occurrence in both natural and aquaculture environments of the eastern Mediterranean. Full article

(This article belongs to the Section Biology and Ecology)

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19 pages, 4187 KB

Open AccessArticle

Assessment of Egg Yolk IgY Antibodies Against Live or Inactivated Aeromonas hydrophila for Polyvalent Passive Immunization in Goldfish (Carassius auratus)

by Pan Cui, Jing Chen, Huihui Xiao, Xixian Che, Shujun Sun, Zijian Ma, Juan Lu, Gaoxiao Xu and Xiang Liu

Fishes 2025, 10(10), 491; https://doi.org/10.3390/fishes10100491 - 1 Oct 2025

Abstract

Egg yolk IgY antibody has significant application potential in aquaculture as a form of passive immunotherapy against various bacterial infections owing to its capacity for large-scale and cost-effective production. In this research, laying hens were immunized with live or inactivated Aeromonas hydrophila to [...] Read more.

Egg yolk IgY antibody has significant application potential in aquaculture as a form of passive immunotherapy against various bacterial infections owing to its capacity for large-scale and cost-effective production. In this research, laying hens were immunized with live or inactivated Aeromonas hydrophila to produce IgY antibodies. Following this, experiments were carried out to assess the passive immune protection rates of the two types of IgY antibodies when used to immunize goldfish (Carassius auratus), which were then infected with A. hydrophila or Aeromonas veronii. ELISA experiments were conducted to demonstrate the interaction between the IgY antibodies and the bacteria. The kidneys of C. auratus were coated on a Luria–Bertani (LB) medium to evaluate bacterial content. The leukocyte phagocytosis was detected by a cell phagocytosis assay. The serum of C. auratus was used to assess the expression of antioxidant factors, and a qRT-PCR was conducted to evaluate the mRNA expression of inflammatory factors in visceral tissue. Furthermore, histopathology and immunofluorescence analysis were performed to evaluate the structural integrity, apoptosis, and DNA damage of visceral tissues. The results indicated that the live or inactivated A. hydrophila IgY antibodies exhibited passive immune protection rates against A. hydrophila and A. veronii and could recognize these two bacteria in vitro. Additionally, these two IgY improved the phagocytic ability of leukocytes, diminished renal bacterial concentration, and decreased the levels of antioxidant factors and mRNA expression of inflammatory factors. Meanwhile, the two IgY antibodies did not cause any pathology of the kidney, spleen, and intestine, and decreased the levels of DNA damage factor (γH2A.X) and cell apoptosis factor (p53) in renal tissue. Therefore, live and inactivated A. hydrophila IgY antibodies can resist bacterial infections, with live bacteria IgY providing greater protection than inactivated bacteria IgY. Further, A. hydrophila is an aquatic pathogen that causes minimal damage to laying hens, and the immunity of live A. hydrophila conforms to animal welfare. Altogether, live A. hydrophila IgY antibody can serve as a polyvalent passive immune vaccine candidate in aquaculture. Full article

(This article belongs to the Section Welfare, Health and Disease)

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18 pages, 3000 KB

Open AccessArticle

Effect of Shading Ratio on Japanese Sea Bass (Lateolabrax japonicus) and Asian Sea Bass (Lates calcarifer) Aquaculture

by Yao-Chen Lee, I-Pei Kuo, Yung-Ting Chung and Shuenn-Der Yang

Fishes 2025, 10(10), 490; https://doi.org/10.3390/fishes10100490 - 1 Oct 2025

Abstract

Floating photovoltaic arrays on ponds may alter thermal and optical conditions that are relevant to aquaculture performance. This study compared 0% and 40% surface shading in two outdoor earthen-pond trials, one with Asian sea bass (Lates calcarifer) and one with Japanese [...] Read more.

Floating photovoltaic arrays on ponds may alter thermal and optical conditions that are relevant to aquaculture performance. This study compared 0% and 40% surface shading in two outdoor earthen-pond trials, one with Asian sea bass (Lates calcarifer) and one with Japanese sea bass (Lateolabrax japonicus). Temperature was logged hourly and summarized as daily means; water quality was sampled biweekly; fish were measured repeatedly, with endpoint growth compared within species. The result shows that shading lowered pond temperature and the diurnal temperature range and reduced the number of days above species benchmark temperatures. Indicators associated with phytoplankton, including suspended solids and chlorophyll a, were lower under shading, whereas dissolved inorganic nutrients were higher. In the Japanese sea bass trial, dissolved oxygen was higher without shading. Final body weight did not differ between treatments within either trial, but survival was higher with 40% shading. Principal component analysis and permutational multivariate analysis of variance indicated a treatment signal in multivariate water quality. Because the trials occurred in different years with one pond per treatment, inference was restricted to contrasts within each species. Overall, moderate surface shading cooled ponds and altered water quality without reducing growth. Full article

(This article belongs to the Section Sustainable Aquaculture)

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16 pages, 42318 KB

Open AccessArticle

Effects of Dietary Carbohydrate Levels on Growth Performance, Antioxidant Capacity, and Hepatointestinal Health in Schizopygopsis younghusbandi

by Tao Ye, Mingfei Luo, Zhihong Liao, Wenrui Zhang, Xingyu Gu, Xuanshu He, Haiqi Pu, Xiaomin Li, Benhe Zeng and Jin Niu

Fishes 2025, 10(10), 489; https://doi.org/10.3390/fishes10100489 - 1 Oct 2025

Abstract

Schizopygopsis younghusbandi is an endemic and ecologically important fish species on the Tibetan Plateau. However, its dietary carbohydrate requirement remains unexplored, limiting the development of cost-effective and physiological-friendly artificial feed. This study investigated the effects of different dietary carbohydrate levels on the growth [...] Read more.

Schizopygopsis younghusbandi is an endemic and ecologically important fish species on the Tibetan Plateau. However, its dietary carbohydrate requirement remains unexplored, limiting the development of cost-effective and physiological-friendly artificial feed. This study investigated the effects of different dietary carbohydrate levels on the growth performance, antioxidant capacity, and hepatointestinal morphology of S.younghusbandi. Six experimental diets were formulated with graded carbohydrate levels of 9% (C9), 12% (C12), 15% (C15), 18% (C18), 21% (C21), and 24% (C24). A total of 720 fish (initial weight 37.49 ± 0.25 g) were randomly allocated to six groups in quadruplicate (30 fish per replicate) and reared in tanks (0.6 m × 0.5 m × 0.4 m) for 8 weeks. Results demonstrated that the diet in the C12 group significantly improved weight gain rate (WGR), specific growth rate (SGR), and feed conversion ratio (FCR) (p < 0.05). Regression fitting analysis on growth performance indicated that the optimal carbohydrate level ranged from 10.42% to 10.49%. Additionally, the C12 group exhibited enhanced total superoxide dismutase (T-SOD) activities and reduced malondialdehyde (MDA) content in the liver, along with reduced interleukin-1β (IL-1β) levels in the serum (p < 0.05). Histological analysis revealed superior hepatointestinal integrity in the C12 group, characterized by lower hepatic lipid droplet accumulation, reduced vacuolation, decreased hepatosomatic index (HSI) (p < 0.05), as well as higher intestinal villus height and muscle thickness (p < 0.05). In conclusion, the C12 group optimally enhanced the growth, antioxidant response, and hepatointestinal health of S. younghusbandi, indicating that the suitable dietary carbohydrate level for this species is 12%. Full article

(This article belongs to the Section Nutrition and Feeding)

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15 pages, 1849 KB

Open AccessArticle

Embryonic and Larval Development of an Interspecific Grouper Backcross Between the Kelp Grouper (Epinephelus moara) ♀ and KGGG (E. moara ♀ × E. lanceolatus ♂) ♂

by Yidan Xu, Yongsheng Tian, Shihao Wang, Tangtang Ding, Linna Wang, Zhentong Li, Linlin Li and Yang Liu

Fishes 2025, 10(10), 488; https://doi.org/10.3390/fishes10100488 - 1 Oct 2025

Abstract

Backcrossing serves as an effective tool for interspecific gene introgression, facilitating germplasm improvement. To develop superior grouper aquaculture varieties, in this study, a backcrossed breed was constructed by crossing a male hybrid grouper, KGGG (Epinephelus moara ♀ × E. lanceolatus ♂), with [...] Read more.

Backcrossing serves as an effective tool for interspecific gene introgression, facilitating germplasm improvement. To develop superior grouper aquaculture varieties, in this study, a backcrossed breed was constructed by crossing a male hybrid grouper, KGGG (Epinephelus moara ♀ × E. lanceolatus ♂), with a female parent kelp grouper (KG; E. moara). Here, we observed embryonic, larval development, and morphological changes in KG × KGGG. Additionally, the total length and body weight of the backcrossed breed and maternal parent were compared at 160 d post hatching (dph). The results showed that fertilization and the hatching rate were 73.23 ± 4.23% and 51.74 ± 3.67%, respectively, and the egg size was 0.89 ± 0.03 mm. Hatching occurred 23:19 h after fertilization at 25 ± 1 °C, and the newly hatched larvae were 1.94 ± 0.13 mm in length. Furthermore, at 160 dph, the total length and body weight of the backcrossed breed were 1.2-fold and 1.9-fold greater, respectively, when compared with those of the maternal parent. Importantly, it is possible that backcrossed KG × KGGG could become a dominant strain in grouper aquaculture practices. Full article

(This article belongs to the Special Issue Germplasm Resources and Genetic Breeding of Aquatic Animals)

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13 pages, 6786 KB

Open AccessArticle

Morphological Analysis of the Intestine in Yangtze Sturgeon (Acipenser dabryanus) During Development

by Luyun Ni, Xiaoyun Wu, Feiyang Li, Qiaolin Zou, Jun Du, Jiansheng Lai and Ya Liu

Fishes 2025, 10(10), 487; https://doi.org/10.3390/fishes10100487 - 1 Oct 2025

Abstract

This study aimed to investigate the histological features of the intestine of Acipenser dabryanus from 1 to 15 months of age via HE staining, AB-PAS staining, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The intestine of A. dabryanus comprises the duodenum, [...] Read more.

This study aimed to investigate the histological features of the intestine of Acipenser dabryanus from 1 to 15 months of age via HE staining, AB-PAS staining, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The intestine of A. dabryanus comprises the duodenum, spiral valve intestine, and rectum. With age, the duodenal diameter and mucosal/muscular layer thickness increased, the spiral valve intestine’s mucosa thickened and protrusions formed networks, and the rectal diameter enlarged. Abundant mucus cells, predominantly type IV, were found in the duodenum, spiral valve intestine, and rectum of A. dabryanus at different ages by AB-PAS staining. Our study confirmed the presence of ciliated columnar cells (with ‘9 + 2’ cilia structure) with orderly arranged cilia at their apices in the mucosal epithelium of A. dabryanus’s duodenum, spiral valve intestine, and rectum for the first time, as shown by SEM and TEM. The presence of spiral valves and ciliated columnar cells in the intestinal structure of A. dabryanus highlights its unique features and evolutionary significance. These findings highlight A. dabryanus’s unique intestinal features and evolutionary significance, providing a basis for scientific feed formulation and enhancing our understanding of the histological characteristics of the sturgeon intestine. Full article

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17 pages, 1269 KB

Open AccessArticle

Mutual Effects of Carassius carassius and Microcystis aeruginosa on Growth Dynamics and Water Quality

by Zhenjiang Yang, Guoxi Li, Jianhua Wang, Jianshe Zhou, Wanliang Wang and Jiangtao Guo

Fishes 2025, 10(10), 486; https://doi.org/10.3390/fishes10100486 - 1 Oct 2025

Abstract

An experimental study was conducted in the laboratory to investigate the interactive effects of fish and algae on growth patterns and water quality. Body length and body weight of Carassius carassius, Microcystis aeruginosa (M. aeruginosa) density, and concentrations of nutrients [...] Read more.

An experimental study was conducted in the laboratory to investigate the interactive effects of fish and algae on growth patterns and water quality. Body length and body weight of Carassius carassius, Microcystis aeruginosa (M. aeruginosa) density, and concentrations of nutrients were monitored continuously over a period of 92 days. It was noted that fish growth was significantly higher in the absence of M. aeruginosa compared to its presence (p < 0.05). This can be partly attributed to toxin production by M. aeruginosa. The densities and growth rates of M. aeruginosa in groups with Carassius carassius were significantly higher than those in fishless groups (p < 0.05), and this was attributable to fish metabolism and bioturbation, which led to a considerable increase in ammonia and total dissolved nitrogen concentrations, as well as a significant impact on proportions of nutrients. The growth rate of Carassius carassius firstly increased and then decreased with increasing M. aeruginosa densities, and a quantitative relationship was established using the Gompertz equation and Logistic equation (R² = 0.914–0.955). Based on the above results, we concluded that interactions between fish and algae are greatly related to their consequences on water qualities, by employing equations, a more detailed interpretation of the processes occurring in the fish–algae system can be achieved. Full article

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18 pages, 2117 KB

Open AccessArticle

Feeding Ecology and Reproductive Biology of the Common Smooth-Hound Shark Mustelus mustelus (Linnaeus, 1758) off the Coast of Türkiye

by Uğur Özden and Erhan Irmak

Fishes 2025, 10(10), 485; https://doi.org/10.3390/fishes10100485 - 1 Oct 2025

Abstract

Sharks play critical roles in marine ecosystems as apex or mesopredators, regulating trophic dynamics and ecosystem stability. However, their populations are increasingly threatened due to overexploitation caused by targeted fisheries, bycatch, and illegal activities. This study investigates the feeding ecology and reproductive biology [...] Read more.

Sharks play critical roles in marine ecosystems as apex or mesopredators, regulating trophic dynamics and ecosystem stability. However, their populations are increasingly threatened due to overexploitation caused by targeted fisheries, bycatch, and illegal activities. This study investigates the feeding ecology and reproductive biology of the shark species Mustelus mustelus, which has been heavily fished across the Mediterranean, leading to significant population declines. A total of 333 specimens were collected between October 2019 and October 2022 from Türkiye’s Aegean Sea, Sea of Marmara, and Levantine Sea coasts. The total lengths of the specimens ranged from 42.1 to 173.0 cm, with an average of 73.5 cm ± 26.8, and their weights ranged from 205 to 22,470 g, with an average of 1840.2 g ± 2525.5. Stomach content analyses revealed that M. mustelus is a benthic predator with a broad diet. Regional and size-based comparisons indicated that crustaceans were the primary food source, followed by teleost fish and mollusks. Ontogenetic dietary shifts were evident, with juveniles feeding predominantly on crustaceans, while adults consumed more teleost fish and mollusca. The reproductive biology analysis showed placental viviparity in M. mustelus, with the smallest observed mature male measuring 75 cm TL and the smallest observed pregnant female measuring 96 cm TL. The uterine fecundity of pregnant females ranged from 8 to 29 embryos. Additionally, the pupping season of M. mustelus in the Aegean Sea was found to occur in March and April. M. mustelus populations have declined dramatically in the western Mediterranean and in many other parts of their range. The scarcity of data on this species in the eastern Mediterranean basin, including Türkiye, is noteworthy. Therefore, this study investigated the populations in the study area from a bioecological perspective and provides fundamental data to support the development of conservation strategies for the species. Full article

(This article belongs to the Section Biology and Ecology)

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14 pages, 3946 KB

Open AccessArticle

Histopathological and Molecular Insights into Grass Carp Kidney Responses to Co-Infection with Aeromonas hydrophila and Aeromonas veronii

by Yifei Zhou, Ruijun Zhu, Lingli Xie, Wenyao Lv, Xinyue Wang, Mengzhou Wu, Xiaoyan Xu and Junqiang Qiu

Fishes 2025, 10(10), 484; https://doi.org/10.3390/fishes10100484 - 29 Sep 2025

Abstract

Grass carp (Ctenopharyngodon idella), a key species in freshwater aquaculture, is particularly vulnerable to opportunistic pathogens, including Aeromonas hydrophila and Aeromonas veronii. While the pathogenic mechanisms of individual infections have been extensively characterized, the host immune responses during co-infection remain [...] Read more.

Grass carp (Ctenopharyngodon idella), a key species in freshwater aquaculture, is particularly vulnerable to opportunistic pathogens, including Aeromonas hydrophila and Aeromonas veronii. While the pathogenic mechanisms of individual infections have been extensively characterized, the host immune responses during co-infection remain poorly understood. This research explored the renal pathological alterations and transcriptomic shifts in grass carp subjected to simultaneous infection by A. hydrophila and A. veronii. Mortality occurred as early as 24 h post-challenge, ultimately reaching a cumulative death rate of 65%. Quantitative analysis of renal bacterial burden revealed a marked increase in colonization at 3 days post-infection (dpi). The histopathological assessment showed progressive kidney damage, including tubular collapse, epithelial necrosis, interstitial edema, and widespread epithelial desquamation, with the most severe lesions observed at 5 dpi and partial signs of recovery by 7 dpi. A total of 1106 and 472 genes were found to be differentially expressed at 1 and 5 dpi, respectively, based on transcriptome profiling. The functional enrichment analysis indicated that the differentially expressed genes (DEGs) were mainly involved in the complement and coagulation cascade pathways. Notably, the immune-related genes exhibited a biphasic trend, with predominant downregulation at 1 dpi followed by marked upregulation by 5 dpi, indicating dynamic changes in immune modulation during co-infection. These results provide new insights into host responses during dual bacterial infections in fish and may inform disease prevention strategies in aquaculture. Full article

(This article belongs to the Section Welfare, Health and Disease)

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18 pages, 3452 KB

Open AccessArticle

Numerical Simulation of Aquaculture-Derived Organic Matter Sedimentation in a Temperate Intensive Aquaculture Bay Based on a Finite-Volume Coastal Ocean Model

by Jing Fu, Ran Yu, Qingze Huang, Sanling Yuan and Jin Zhou

Fishes 2025, 10(10), 483; https://doi.org/10.3390/fishes10100483 - 28 Sep 2025

Abstract

In this study, a numerical model consisting of high-resolution hydrodynamic and Lagrangian particle tracking modules based on the Finite-Volume Coastal Ocean Model framework was established to simulate the hydrodynamic conditions and characteristics of the sedimentation of aquaculture-derived organic matter (AOM) from cage aquaculture [...] Read more.

In this study, a numerical model consisting of high-resolution hydrodynamic and Lagrangian particle tracking modules based on the Finite-Volume Coastal Ocean Model framework was established to simulate the hydrodynamic conditions and characteristics of the sedimentation of aquaculture-derived organic matter (AOM) from cage aquaculture in Sansha Bay. The results showed that Sansha Bay was characterized by regular semidiurnal tides and large tidal ranges. Reciprocating currents with main currents directed northward and southward during the rising and falling tides, respectively, predominated the main channels of the bay. Residual feed had larger settling velocities than feces. The maximal dispersion distances of residual feed and feces during the spring tide were 217.1 and 1805.7 m, respectively, three times those during the neap tide (74.2 and 675.6 m, respectively). During the spring tide, the largest dispersion distance of AOM occurred at the rush moment. The AOM movement trajectories were mainly controlled by the main currents. Both the tidal structure and current characteristics affected the AOM sedimentation in Sansha Bay. The sedimentation characteristics of AOM were unrelated to feeding intensity. The results of simulations agreed with the field observations in this study, suggesting that the estimated model had a good accuracy and sensitivity. Full article

(This article belongs to the Special Issue New Technologies for Improving Fisheries and Aquaculture Production and Management)

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17 pages, 1705 KB

Open AccessArticle

Effect of Dietary Proline on the Growth Performance, Collagen Deposition, and Texture Quality of Sea Cucumbers’ Body Wall (Apostichopus japonicus)

by Rujian Xu, Zitong Wang, Haijing Liu, Ruixue Li, Xianyu Wang, Hongbing Yang, Jun Ding, Yaqing Chang and Rantao Zuo

Fishes 2025, 10(10), 482; https://doi.org/10.3390/fishes10100482 - 26 Sep 2025

Abstract

Sea cucumber (Apostichopus japonicus) is an important economically cultured species in the northern coastal regions of China. Its body wall is rich in collagen, which directly determines product quality and market value. However, with the expansion of aquaculture scale, issues such [...] Read more.

Sea cucumber (Apostichopus japonicus) is an important economically cultured species in the northern coastal regions of China. Its body wall is rich in collagen, which directly determines product quality and market value. However, with the expansion of aquaculture scale, issues such as insufficient collagen deposition have led to inconsistent quality among cultured individuals. Therefore, there is an urgent need to improve growth performance and body wall quality through nutritional regulation. As functional nutrients, amino acids play key roles in collagen synthesis, yet relevant research on A. japonicus remains limited. This study was conducted to investigate the effects of dietary proline on the growth performance, body wall collagen deposition and organoleptic quality of sea cucumber (initial body weight: 30.20 ± 2.02 g). Three kinds of feed with equal levels of nitrogen and other lipids, and supplemented with different concentrations of proline (0%, 1.5%, 3%) in the basal diet, were named P0, P1.5, and P3, and the experiment was conducted for 60 days. The results showed that supplementation with 3% proline significantly increased final body weight and weight gain rate (p < 0.05), reaching 66.39 g and 115.30%, respectively. Collagen content in the body wall increased by approximately 18.5% compared to the control group. Histological analysis of the body wall showed that the collagen fibers in the P1.5 and P3 groups were thicker, with an increased proportion of type I collagen. Texture profile analysis indicated that hardness, cohesiveness, and chewiness were significantly improved in the P3 group (p < 0.05). In summary, supplementation with 1.5% and 3% proline effectively enhanced growth, collagen deposition, and body wall quality. Compared to the P0 group, the relative expression levels of collagen type I alpha 2 chain (COL1A1), Sma- and Mad-related protein 1(SMAD1), and sp-smad2/3 (SMAD2/3) in the body wall tissue were significantly upregulated in both the P1.5 and P3 groups (p < 0.05). Full article

(This article belongs to the Special Issue Advances in Aquaculture Feed Additives)

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14 pages, 4048 KB

Open AccessArticle

Noctilucent Crab Pots in the Yellow Sea, China: Field Evidence for Catch Efficiency Enhancement and Sustainable Crab Fishery Practices

by Wei Liu, Minghua Min, Zhongqiu Wang, Yongli Liu, Lumin Wang and Xun Zhang

Fishes 2025, 10(10), 481; https://doi.org/10.3390/fishes10100481 - 26 Sep 2025

Abstract

Artificial light has been shown to enhance the fishing efficiency of fishing gear by attracting marine organisms. This study introduces a novel approach by incorporating noctilucent materials into crab pots and evaluates their effects on catch performance. Based on the crab pots commonly [...] Read more.

Artificial light has been shown to enhance the fishing efficiency of fishing gear by attracting marine organisms. This study introduces a novel approach by incorporating noctilucent materials into crab pots and evaluates their effects on catch performance. Based on the crab pots commonly used on the coast, four types of crab pots were tested: ordinary crab pots (Con-pot), ordinary crab pots equipped with noctilucent sticks (Exp-pot 1), crab pots equipped with noctilucent nets (Exp-pot 2), and crab pots equipped with both noctilucent nets and sticks (Exp-pot 3). The results showed that the noctilucent material exhibits 6 h persistent emission in darkness after just 10 min of solar charging. Exp-pot 3 could significantly enhance fishing efficiency, which increased by 63.84% compared to the Con-pot. The proportion of crabs in Exp-pot 3 was the highest (86.35%), and the individual weight of crabs in Exp-pot 3 was the heaviest (61.5 g), which was 38.30% heavier than that in the Con-pot. Notably, Exp-pots 2 and 3 demonstrated superior selectivity with higher W₅₀ values (53.01 g and 54.49 g), narrower SRs (33.04–72.98 g and 32.95–76.03 g), effectively balancing target catch retention with undersized crab release, indicated that noctilucent nets exhibited stronger weight selectivity for crabs compared to noctilucent sticks. These results demonstrate that functional materials have broad potential applications in fishing gear, which could enhance the catch efficiency and individual size of crab caught. Full article

(This article belongs to the Special Issue Sustainable Fisheries Dynamics)

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15 pages, 478 KB

Open AccessArticle

Nitrogen Budget in Yellow-Tail Lambari Monoculture and Integrated Aquaculture

by Dalton Belmudes, Andre Z. Boaratti, Paulo V. L. Mantoan, Aline M. Marques, Julia R. C. Ferreira, Patricia Moraes-Valenti, Dallas L. Flickinger and Wagner C. Valenti

Fishes 2025, 10(10), 480; https://doi.org/10.3390/fishes10100480 - 26 Sep 2025

Abstract

This study quantified nitrogen (N) inputs by water, feed, animals, and atmospheric gas and outputs by water, harvested animals, sediments, and gas emissions in earthen ponds used for the monoculture and integrated cultures of yellow-tail lambari (Astyanax lacustris), Amazon River prawn [...] Read more.

This study quantified nitrogen (N) inputs by water, feed, animals, and atmospheric gas and outputs by water, harvested animals, sediments, and gas emissions in earthen ponds used for the monoculture and integrated cultures of yellow-tail lambari (Astyanax lacustris), Amazon River prawn (Macrobrachium amazonicum), and curimbata (Prochilodus lineatus), and evaluated whether epibenthic species improve N retention in harvested biomass. Three systems with four replicates were tested, lambari monoculture (L), lambari–prawn (LP), and lambari–prawn–curimbata (LPC), stocked at 50, 25, and 13 individuals m⁻², respectively. Feed N was the major input (67–75%), followed by inlet water (19–30%). Harvested biomass represented 20–23% of total outputs, sediments 25–33%, and gaseous emissions 7–29%, while outlet water contributed <3%. N lost through seepage was highest in L (70.5 ± 22.9 kg N ha⁻¹). N₂ ebullition increased with benthic species, from 10.4 ± 10.6 kg N ha⁻¹ (L) to 72.1 ± 32.4 kg N ha⁻¹ (LPC). N recovered in lambari was 43.2 ± 7.4 kg N ha⁻¹ in LPC, 36 ± 8.6 in L, and 33 ± 5.6 in LP. Considering all species, recovery of dietary N increased from 20.0 ± 4.3% (L) to 35.0 ± 5.9% (LPC), and recovery from all inputs rose from 13.0 ± 2.2% to 18.0 ± 3.4%. Integrated systems, particularly LPC, enhanced N retention in biomass and reduced environmental losses. Full article

(This article belongs to the Special Issue Integrated Multi-Trophic Aquaculture (IMTA))

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